Climate change is affecting people, infrastructure, and ecosystems across Canada. Although the impacts are currently most pronounced in coastal regions, people and infrastructure everywhere are at risk. Many communities and infrastructure built in floodplains are at increased risk of flooding due to the projected effects of climate change and other non-stationary factors such as wildfires, dams, and other anthropogenic changes. In response to these risks, both the Canadian federal and provincial governments are mobilizing to identify and respond to flood hazards.

The goal of flood hazard mapping is to provide the first step towards tangible improvements to public safety. Real improvement comes from planning, analyzing, and developing adaptation and mitigation projects that are successfully implemented in communities.

Once a hazard has been identified, we often conduct flood risk assessments that evaluate the path of a potential flood and quantify the damages expected to people, infrastructure, and assets (such as houses, parks, or culturally significant places). This information helps secure funding for adaptation and mitigation projects by providing a quantifiable return on investment, and helps decision-makers prioritize adaptation or mitigation projects or areas.

Custom-built GIS tools are a key part of identifying flood hazards and determining adaptation and mitigation strategies

To facilitate flood hazard and flood risk assessments, Associated Engineering uses custom-built GIS tools to identify flood hazards. With the development of new, custom-built processes, work that was previously labour and time intensive can now be completed more efficiently. This allows our team to focus on collaborating with our clients to discuss risks and mitigation strategies, and design solutions that provide tangible improvements to public safety and flood risk reduction.

These tools have been used successfully on projects, and more are in active development to expand our suite of modelling and mapping tools. Additionally, our team is working on a research assignment to further optimize flood hazard mapping and make analysis more efficient and effective.

Automation in GIS data processing, including the tools discussed below, allows our team to more efficiently identify flood hazards so that we can focus on implementing solutions.

The Tools

Our team developed these automated, GIS data-processing tools to support flood mapping for 165 kilometres of rivers in BC, as part of the Flood Hazard Identification and Mapping Program. The visuals shown are not final; final mapping will be available online within one year of project completion. The tools address the challenges of providing large-scale, high-detail flood mapping. Some of these tools include:

Survey Processing and DEM Development: Linearizing, interpolating, and overlaying bathymetric survey with LiDAR to create a representative surface for use in hydraulic modelling. These automated methods help preserve data and expedite the processing time.

Model Results Extraction and Processing: Automated comparison and combination of result surfaces allows for robust analysis of multi-hazard scenarios.

Automated Generation and Review of Legal Flood Maps: Application of required freeboard and preparation of flood construction levels using a data-driven methodology.

About the Authors:

Andromeda MacIsaac, P.Eng. is Water Resources Engineer in our Vancouver office. She has 11 years of experience in hydrology, hydraulics, hydrologic/hydraulic modelling, and integrated water resources management. Her expertise includes modelling, analysis, and design of minor and major surface water systems and related hydraulic structures, including flood-plain mapping, existing system capacity analysis, fish passage structures, bridge sizing, stormwater best management practices, inflow/infiltration, and scour protection.

Chloe Sirges, E.I.T. is a Water Resources Engineer in our Vancouver office. Her water resources experience includes hydraulic modelling, flood-risk assessment and mitigation, site inspection, bridge scour condition assessments, and coastal work. Chloe is proficient in GIS data processing and flood-plain mapping

The post Automation in GIS Data Processing helps identify flood hazards and determine possible responses first appeared on Associated Engineering.

In recent years, the City of Lethbridge has experienced several significant rainfall events, resulting in roadway flooding and damage to infrastructure in Alberta’s fourth largest city. Extreme rain events in 2020 further highlighted areas prone to flooding and the need for operational improvements to the City’s stormwater management system.

The City’s stormwater infrastructure consists of approximately 465 kilometres of stormwater pipe, 6,000 stormwater manholes, and many stormwater management facilities. To better understand and help plan for improvements to their stormwater management system, the City of Lethbridge wanted to develop a stormwater model of the system, and retained Associated Engineering to undertake this work. 

Our approach allows the team to focus additional effort on quality control and quality assurance of the models, as well as interpretation of model results

Project Manager, Adam McDonald, tells us, “The City sought the ability to evaluate their stormwater management system against design rainfall events to determine the conditions contributing to flooding. They also wanted to be able to confirm drainage capacities in new areas being developed, and where new areas will be connecting to the existing system.”

Our team’s tasks included data collection and review; development of a geographic information system (GIS) data model and model development templates; data quality control; design rainfall event selection and design; climate change rainfall forecast; development of existing system one-dimension by one-dimension drainage models; quality assurance and quality control reviews; existing system analysis and risk assessment; development of improvement concepts for five top-ranked locations; cost estimates; and reporting.

Model files are large in scope and incorporate all of the drainage infrastructure. As a result, the full City of Lethbridge model has been divided into separate models to streamline model run times. 

The development of detailed stormwater management models using traditional methods is an extremely labour intensive exercise. Associated Engineering’s approach uses GIS tools and programming to facilitate development of key parts of the model. Associated’s team developed one-dimension by one-dimension (1D-1D), dual drainage models of the City’s drainage system, analyzing stormwater flow in the storm sewer system as well as surface drainage. The models needed to cover all of Lethbridge and be sufficiently detailed to predict flooding due to minor system (e.g. gutters, catch basins, and storm sewers) surcharge and major system flows (e.g. streets, streams, channels, and ponds).

Adam explains, “The model development required significant data analysis and pre-processing to verify data.” As a value-added exercise, Associated Engineering committed to additional data input, feature digitization, and GIS quality control.

“Our project team developed automated custom queries for GIS data processing, comparing the data by proximity to help identify and flag any issues. Any missing data was interpolated and flagged for future identification.”

Throughout the project, the team looked for opportunities to further refine our standardized approach to model building and made significant improvements to the GIS programming that is used to streamline the process.

The model results were validated against anecdotal information of historical flooding, matched known flooding locations, and, in some cases, the results of other stormwater models which provided confidence in the accuracy of results produced.

Climate change adaptation was a key consideration on the project. The team provided the City with models that incorporate the design rain events, as well as historical return frequency events, and forecasted climate change events. The forecasted climate change rainfall events will enable the City to quantify the requirements to manage current and future flood risk affected by climate change impacts. 

The team also identified five areas for improvements to mitigate flooding. To assist the City with prioritizing improvements, we recommended that the City work with stakeholders to develop a customized definition of the preferred level of service for each area, based on a triple bottom line approach. The existing system models should then be used to develop a master drainage plan that takes a holistic look at flood risk and mitigation plans and thus inform investment in infrastructure and capital expenditures.

The project is in its final stages, and will be complete early in 2022. Our key personnel on this project included Adam McDonald, Andrew Rushworth, Carmen Janzen, and Laurel Richards. 

The post Predictive citywide stormwater models help protect Lethbridge’s infrastructure first appeared on Associated Engineering.